uwsgi long timeouts - sockets

Question

I am using ubuntu 12, nginx, uwsgi 1.9 with socket, django 1.5.
Config:
[uwsgi]
base_path = /home/someuser/web/
module = server.manage_uwsgi
uid = www-data
gid = www-data
virtualenv = /home/someuser
master = true
vacuum = true
harakiri = 20
harakiri-verbose = true
log-x-forwarded-for = true
profiler = true
no-orphans = true
max-requests = 10000
cpu-affinity = 1
workers = 4
reload-on-as = 512
listen = 3000
Client tests from Windows7:
C:\Users\user>C:\AppServ\Apache2.2\bin\ab.exe -c 255 -n 5000 http://www.someweb.com/about/
This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright 2006 The Apache Software Foundation, http://www.apache.org/
Benchmarking www.someweb.com (be patient)
Completed 500 requests
Completed 1000 requests
Completed 1500 requests
Completed 2000 requests
Completed 2500 requests
Completed 3000 requests
Completed 3500 requests
Completed 4000 requests
Completed 4500 requests
Finished 5000 requests
Server Software: nginx
Server Hostname: www.someweb.com
Server Port: 80
Document Path: /about/
Document Length: 1881 bytes
Concurrency Level: 255
Time taken for tests: 66.669814 seconds
Complete requests: 5000
Failed requests: 1
(Connect: 1, Length: 0, Exceptions: 0)
Write errors: 0
Total transferred: 10285000 bytes
HTML transferred: 9405000 bytes
Requests per second: 75.00 [#/sec] (mean)
Time per request: 3400.161 [ms] (mean)
Time per request: 13.334 [ms] (mean, across all concurrent requests)
Transfer rate: 150.64 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 0 8 207.8 1 9007
Processing: 10 3380 11480.5 440 54421
Waiting: 6 1060 3396.5 271 48424
Total: 11 3389 11498.5 441 54423
Percentage of the requests served within a certain time (ms)
50% 441
66% 466
75% 499
80% 519
90% 3415
95% 36440
98% 54407
99% 54413
100% 54423 (longest request)
I have set following options too:
echo 3000 > /proc/sys/net/core/netdev_max_backlog
echo 3000 > /proc/sys/net/core/somaxconn
So,
1) I make first 3000 requests super fast. I see progress in ab and in uwsgi requests logs -
[pid: 5056|app: 0|req: 518/4997] 80.114.157.139 () {30 vars in 378 bytes} [Thu Mar 21 12:37:31 2013] GET /about/ => generated 1881 bytes in 4 msecs (HTTP/1.0 200) 3 headers in 105 bytes (1 switches on core 0)
[pid: 5052|app: 0|req: 512/4998] 80.114.157.139 () {30 vars in 378 bytes} [Thu Mar 21 12:37:31 2013] GET /about/ => generated 1881 bytes in 4 msecs (HTTP/1.0 200) 3 headers in 105 bytes (1 switches on core 0)
[pid: 5054|app: 0|req: 353/4999] 80.114.157.139 () {30 vars in 378 bytes} [Thu Mar 21 12:37:31 2013] GET /about/ => generated 1881 bytes in 4 msecs (HTTP/1.0 200) 3 headers in 105 bytes (1 switches on core 0)
I dont have any broken pipes or worker respawns.
2) Next requests are running very slow or with some timeout. Looks like that some buffer becomes full and I am waiting before it becomes empty.
3) Some buffer becomes empty.
4) ~500 requests are processed super fast.
5) Some timeout.
6) see Nr. 4
7) see Nr. 5
8) see Nr. 4
9) see Nr. 5
....
....
Need your help

Answer 1

check with netstat and dmesg. You have probably exhausted ephemeral ports or filled the conntrack table.